FAILED: patch "[PATCH] io_uring: don't take files/mm for a dead task" failed to apply to 5.10-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 621fadc22365f3cf307bcd9048e3372e9ee9cdcc Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Mon, 11 Jan 2021 04:00:31 +0000
Subject: [PATCH] io_uring: don't take files/mm for a dead task

In rare cases a task may be exiting while io_ring_exit_work() trying to
cancel/wait its requests. It's ok for __io_sq_thread_acquire_mm()
because of SQPOLL check, but is not for __io_sq_thread_acquire_files().
Play safe and fail for both of them.

Cc: stable@vger.kernel.org # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7af74c1ec909..b0e6d8e607a3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1106,6 +1106,9 @@ static void io_sq_thread_drop_mm_files(void)
 
 static int __io_sq_thread_acquire_files(struct io_ring_ctx *ctx)
 {
+	if (current->flags & PF_EXITING)
+		return -EFAULT;
+
 	if (!current->files) {
 		struct files_struct *files;
 		struct nsproxy *nsproxy;
@@ -1133,6 +1136,8 @@ static int __io_sq_thread_acquire_mm(struct io_ring_ctx *ctx)
 {
 	struct mm_struct *mm;
 
+	if (current->flags & PF_EXITING)
+		return -EFAULT;
 	if (current->mm)
 		return 0;